Prior to 1951, whenever surgeons needed to perform cardiac surgery, the only option was for them to operate on the beating heart as it continued to pump blood. On Apr. 5, 1951, Dr. Clarence Dennis conducted the first temporary takeover of both the heart and lung functions. Unfortunately, the patient did not survive due to a congenital heart defect. However, this stirred the interest of other doctors throughout the world, and soon after Dr. John Gibbon Jr. completed the first successful human heart surgery in 1953.
Now, over fifty years later, cardiopulmonary bypass (CPB) surgery is routinely done for patients that require cardiac surgery. Even though general surgical complications from cardiopulmonary bypass aren't frequent, when they occur, these complications are associated with a high mortality. A study was done at the University of Virginia Health Sciences Center in which 1831 patients had undergone CPB for a three-year period. There were 39 general surgical complications defined (incidence of ˜2.0%) and there were 14 deaths—a mortality of 38.9% out of the patients with surgical complications.
Unfortunately, there are limited resources available to investigate side effects of CPB on certain populations. These populations include the elderly, those with specific genetic dispositions, such as diabetes, and patients with other illnesses. Furthermore, human CPB demographics are changing. There are currently more patients with genetic predispositions and patients who are getting older and sick. More patients have other health issues as well. There needs to be a miniaturized model to study these impacts on a cellular and molecular level. Mice represent the perfect study model because they are inexpensive, can be inbred, genetically altered and have a similar anatomy to that of humans.
Designs in the prior art include thin film centrifugal oxygenators, membrane oxygenators, and a bubble oxygenator. The bubble oxygenator has been shown to be effective in bypass circuits for small animal models, but it requires a large reservoir of blood and cannot be sufficiently miniaturized. Similarly, the membrane oxygenator has also been shown to be effective in small animal bypass circuits for rats, but produces a prime volume an order of magnitude greater than is needed for mouse testing. However, the length of tubing, and therefore prime volume, needed to oxygenate the blood can be excessive for mouse testing. The thin film centrifugal oxygenator has been shown to be effective and it also has a relatively low prime volume, but the spinning disk and associated moving components are at risk for failing. Furthermore, the uncontrolled nature of hurling blood from a spinning disk necessitates an unsuitably large prime volume to ensure the reservoir stays filled to prevent gas emboli.
It is therefore desirable to provide a device with a sufficiently small prime volume suitable for use in performing cardiopulmonary surgery on mice and other small mammals.